Various techniques are known for establishing a rotating field in an AC motor by providing phase shifted fields in separate windings. Numerous systems are known for providing the phase shift, including various combinations of resistors, capacitors or inductors to store electrical energy and then release it as phase shifted alternating current.
The present invention enables the use of one or more H-switches to provide the desired phase shift for the motor, without energy-storage phasing capacitors or inductors.
H-switches are commonly used in converter-inverters, and cycloconverters, e.g. for frequency conversion. The present invention provides a particularly simple and effective technique for using H-switches to afford the requisite phase shift for starting an AC motor.